High Performance Polylactic Acid/Boron Nitride Thermal Conductive Composite Based on Chaotic Field Melt Extrusion

ABSTRACT Polylactic acid/hexagonal boron nitride (PLA/h‐BN) thermal conductive composites hold broad application prospects owing to their electrical insulation and biodegradability. However, the conventional twin‐screw extruder (TSE) based on shear fields struggles to achieve satisfactory in situ exfoliation of h‐BN and tends to induce severe degradation of the PLA. This paper employed novel perturbation ring elements (PREs) to modify a dual‐speed nontwin screw extruder (NTSE) based on a chaotic field for the large‐scale preparation of high‐performance PLA/h‐BN thermal conductive composite. The results indicate that compared with TSE, NTSE exhibited shorter residence times and a narrower residence time distribution for the material, while the mixing index was significantly improved, which can achieve significantly better in situ exfoliation, dispersion, and distribution of h‐BN in the presence of a lower degradation degree of PLA. Moreover, after the NTSE was further modified with PRE, this phenomenon became more pronounced. Compared with those prepared by TSE, PLA/h‐BN prepared via NTSE‐PRE exhibited in‐plane and through‐plane thermal conductivities increased by 26.6% and 16.9%, respectively, alongside intrinsic viscosity and weight‐average molecular weight elevated by 21.5% and 20.0%, while the Young's modulus after annealing increased by 11.5%. This work provides a novel approach for the large‐scale preparation of biodegradable polymer‐based thermally conductive composites.